Should I replace my Edwardian house floor with concrete?

FreeBear

If you are hell bent on ripping out the wooden floor, look at a foamed glass sub-base finished off with limecrete. The foamed glass will give you insulation, and the limecrete will allow any damp to dissipate. Concrete will just push the damp in to the walls and cause problems in the coming years.

If you want to spend £5K on a new floor, you'd be better off ripping out the concrete section and putting down a suspended timber floor - Add some insulation between the joists, make sure there is plenty of ventilation underneath, and it will out last you.

Doozergirl

Please don't do that. 

You could fully replace the suspended timber a few times over for the same price.  The key is ventilation.  There should be airbricks at front and back to get a through-flow.  Can you do that or is the back completely concreted?  What about the sides?  

Airbricks cost pence.

Some old houses can cope with having a floor concreted, but many won't and the dampness which is under the house gets trapped and sweaty by the plastic damp proof membrane under the concrete and it starts to push up the walls in an attempt to breathe.  When the house is covered in concrete, it finds that very difficult indeed.  They were built with breathable lime in the pointing in the walls and plaster, not impermeable concrete.
 

Modern houses are designed in a particular way; old houses were designed a different way and modern methods don't work well with them.  A house standing for 100-200 years shows that the way they were built works just fine.   The reason for them stopping working is often a modern internvention.  Old houses just need maintaining correctly.  

molly68

Doozergirl said:

Please don't do that. 

You could fully replace the suspended timber a few times over for the same price.  The key is ventilation.  There should be airbricks at front and back to get a through-flow.  Can you do that or is the back completely concreted?  What about the sides?  

Airbricks cost pence.

Some old houses can cope with having a floor concreted, but many won't and the dampness which is under the house gets trapped and sweaty by the plastic damp proof membrane under the concrete and it starts to push up the walls in an attempt to breathe.  When the house is covered in concrete, it finds that very difficult indeed.  They were built with breathable lime in the pointing in the walls and plaster, not impermeable concrete.
 

Modern houses are designed in a particular way; old houses were designed a different way and modern methods don't work well with them.  A house standing for 100-200 years shows that the way they were built works just fine.   The reason for them stopping working is often a modern internvention.  Old houses just need maintaining correctly.  

Thankyou Doozergirl, house is a mid terrace. It looks like there’s no ventilation at the rear as the back of the living room was the original kitchen which was concrete...I could be wrong though.  I’ll definitely get a second opinion from the independent surveyor as he has no affiliation....concrete does not seem a logical option.

Rural_Puppy

This is a really interesting thread. My first thought was avoid a cement floor if you can for the same reasons given by Freebear and Doozergirl - it risks dampness wicking up the walls.
I am interested in opinions on this product: https://www.permagard.co.uk/advice/damp-proofing-walls
Would this work with a cement floor slab to help prevent the water rising up the walls?
Probably only useful if the plan is to redo the interior walls as well?

KiwiCoop

What is the depth of the floor void?  If it is relatively shallow, replacing a suspended timber floor with a solid one can actually reduce damp as you have to excavate down and remove enough soil to make room for the hardcore, blinding, insulation, sub-floor & screed plus you will have a dpm underneath which will run up the side of the slab preventing ingress into the walls.  £2k wouldn't look at it though.

Doozergirl

molly68 said:

Doozergirl said:

Please don't do that. 

You could fully replace the suspended timber a few times over for the same price.  The key is ventilation.  There should be airbricks at front and back to get a through-flow.  Can you do that or is the back completely concreted?  What about the sides?  

Airbricks cost pence.

Some old houses can cope with having a floor concreted, but many won't and the dampness which is under the house gets trapped and sweaty by the plastic damp proof membrane under the concrete and it starts to push up the walls in an attempt to breathe.  When the house is covered in concrete, it finds that very difficult indeed.  They were built with breathable lime in the pointing in the walls and plaster, not impermeable concrete.
 

Modern houses are designed in a particular way; old houses were designed a different way and modern methods don't work well with them.  A house standing for 100-200 years shows that the way they were built works just fine.   The reason for them stopping working is often a modern internvention.  Old houses just need maintaining correctly.  

Thankyou Doozergirl, house is a mid terrace. It looks like there’s no ventilation at the rear as the back of the living room was the original kitchen which was concrete...I could be wrong though.  I’ll definitely get a second opinion from the independent surveyor as he has no affiliation....concrete does not seem a logical option.

If it's done, it's done.  You could look at a positive input ventilation system instead?  

Doozergirl

Rural_Puppy said:

This is a really interesting thread. My first thought was avoid a cement floor if you can for the same reasons given by Freebear and Doozergirl - it risks dampness wicking up the walls.
I am interested in opinions on this product: https://www.permagard.co.uk/advice/damp-proofing-walls
Would this work with a cement floor slab to help prevent the water rising up the walls?
Probably only useful if the plan is to redo the interior walls as well?

It doesn't prevent it.  It keeps it hidden in the brickwork and blocks it from showing through on the plaster side. 

The best solution would be natural insulation and lime plaster inside, and ensuring any pointing outside is also lime.  That allows the walls to breathe properly.

To allow the floor to breath better, you can cut the concrete and floor DPM out a foot around the walls and replace that with glass bead insulation and limecrete as freebear suggested above for a full floor.  

Doozergirl

KiwiCoop said:

What is the depth of the floor void?  If it is relatively shallow, replacing a suspended timber floor with a solid one can actually reduce damp as you have to excavate down and remove enough soil to make room for the hardcore, blinding, insulation, sub-floor & screed plus you will have a dpm underneath which will run up the side of the slab preventing ingress into the walls.  £2k wouldn't look at it though.

Er, no it doesn't prevent ingress into the walls, it does the opposite!  The DPM lapping up the inside of the existing wall means that any excess moisture under the slab is actually forced up the walls because it can't escape from anywhere else. 

If you put an old fashioned plastic mac on over your skin, you'd start to get sweaty pretty quickly.  Your pores are designed to breath to allow moisture to evaporate.  Old houses are exactly the same.  

FreeBear

KiwiCoop said:  you have to excavate down and remove enough soil to make room for the hardcore, blinding, insulation, sub-floor & screed

If the foundations are shallow, as most old properties are, you'd be digging out below the footings - This could cause structural issues if not done correctly (and a concrete floor with DPM is not really appropriate for a period property).

molly68

Thankyou all for your suggestions. This is my first solo house purchase and my budget is mainly for cosmetic repairs. My plan was to fit a engineered wooden floor over both surfaces (not sure if this would work over the wood) lots to think about.